Because of the ever increasing interest in avoiding infection a plurality of disposable safety lancets have been developed, it being ensured with various means that the safety lancet can only be used a single time. Further, there are safety lancets in which the lancet blade only briefly protrudes from an opening in the lancet housing and is immediately retracted again, so that the user and others cannot get into contact with the lancet blade, which has touched the person's blood and can therefore be a potential disease carrier.
Safety lancets of the present type comprises a spring which is compressed and then released. The spring then drives the lancet blade at a great rate inside the lancet housing toward the opening, and owing to the kinetic energy achieved by the spring and the lancet blade the spring extends beyond its equilibrium so that the lancet blade briefly protrudes from the opening. The spring then retracts to its relaxed position in which the lancet blade is retracted from the opening. It is here necessary that the spring is capable of imparting a high rate and thus much kinetic energy to the lancet blade, and a relatively stiff spring is required for this purpose. However, stiff springs tend not to permit any great movement of the free end of the spring with the lancet blade beyond the equilibrium of the spring, and the distance between the maximally extended position of the lancet blade and the retracted position can therefore frequently be so short that the lancet blade when retracted is in an inexpediently advanced position, so that it will be possible to touch the lancet blade with the consequent risk of transmission of infection.
It is therefore desirable that the spring has a long travel beyond its relaxed position following release, enabling a great distance between the maximally extended position of the lancet blade and its retracted position.